Multi-pad, multi-function electrode

ABSTRACT

An electrode having multiple conductive polymer pads for performing multiple, electrical physiological functions from a single set of electrodes with respect to a patient at or about the same time, such as defibrillating, pacing, and monitoring of that patient&#39;s heart, is described. The electrode is advantageously integrated into a cardiac system having stimulating means coupled to the electrode for delivering electrical impulses to the electrode to be used to stimulate the patient&#39;s heart, and monitoring means also coupled to the electrode for receiving and displaying electrical impulses produced by the patient&#39;s heart. The conductive polymers which comprise the pads are optionally inherently adhesive, so that the pads will adhere to a patient&#39;s body over their entire surface area. Moreover, they are rubber-based, will not smear or leave a residue on a patient&#39;s skin, have lower impedance, and depolarize faster compared with present saline-based gels, further contributing to the multi-functional capability. Also, the other impedance enables the voltage generator in the cardiac system of which the electrode is part to deliver a particular current pulse with less voltage, enabling the voltage generator, and the cardiac system in general, to be smaller, more compact, and less costly.

This application is a continuation application of U.S. patentapplication Ser. No. 237,513, filed Aug. 26, 1988, now U.S. Pat. No.4,955,381.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a multi-pad, multi-functionelectrode, and more specifically, to an electrode having multipleconductive polymer pads which enable a single set of electrodes toperform multiple electrical, physiological functions with respect to apatient, such as monitoring and stimulating of the patient's heart, ator about the same time.

2. Background Information

Prior art electrodes have traditionally been single-function electrodeswhich can be divided into two classes according to their function,whether monitoring or stimulation. A monitoring electrode is used totransfer electrical impulses from a patient's body to a cardiac systemwhich usually displays the impulses to permit monitoring of thatpatient's heart condition; a stimulating electrode, on the other hand,is used to deliver stimulating electrical impulses from a cardiac systemto a patient's body to permit either defibrillation or external pacingof that patient's heart.

The prior art monitoring and stimulating electrodes differ quite a bitin their physical characteristics. The monitoring electrode, forexample, is typically 2-4 cm. in diameter with a single 1-2 cm.conductive center pad for receiving electrical impulses from a patient'sheart, and delivering them to a monitor. The stimulating electrode, onthe other hand, at least a stimulating electrode for delivering highenergy to a patient for either defibrillation or external cardiacpacing, is typically 10-14 cm. in diameter with a single 8-12 cm.conductive center pad for delivering electrical impulses to a patient'sheart from a voltage or current generator of a cardiac system.

The majority of prior art electrodes, whether for stimulating ormonitoring, are constructed similarly. They are made of a flexible foambacking attached to a piece of metal foil with a connecting leadattached to the center. The foil in turn is attached to a conductivegel-filled sponge which is surrounded by a ring of flexible adhesivefoam for attachment to a patient's skin.

These prior art electrodes suffer from a number of problems. First, theyare severely limited in their ability to perform multiple electrical,physiological functions with respect to a patient from a single set ofelectrodes. As a result, it is necessary to either perform multipleelectrical, physiological functions sequentially from a single set ofelectrodes, or else use multiple sets of electrodes simultaneously, inorder to deliver multiple electrical, physiological functions to apatient. Each one of these approaches has an associated set of problems.

Sequential defibrillating and monitoring from a single set of prior artelectrodes, although possible, will in many cases necessitate a longwait between the performance of the monitoring and defibrillatingfunctions until the electrodes have depolarized, i.e. discharge storedenergy (see ensuing discussion). This will in many instances result indelays in delivering necessary care to a patient under emergencyconditions, which can have disastrous consequences.

Also, sequential pacing and monitoring from a single set of electrodeswill simply be impossible since a pacing pulse must be administered atleast sixty times per minute, and there will be insufficient timebetween the application of the pacing pulses for the electrodes todepolarize, i.e., discharge energy from the pacing pulses which has beenstored in the electrodes through a process called polarization. Sincethere may be insufficient time for the electrodes to depolarize, i.e.discharge the stored energy, before the electrodes are used to monitor,the stored energy will mask the electrical impulses being received fromthe patient's heart, and accurate monitoring will be impossible.

The theoretical basis for how an electrode stores energy is that theelectrode effectively forms a capacitor, with the metal foil forming oneplate of the "capacitor," the internal "wet" portion of the body formingthe second plate, and the conductive pad (typically a gel-filled sponge)comprising the material placed between the "capacitor" plates. When theelectrode is used to stimulate a patient's heart, and a current pulse isdelivered through the electrode to effectuate either pacing ordefibrillation, the voltage between the "capacitor" plates builds upslowly, typically to levels of several hundred millivolts. The voltagetakes time to build up as the material between the "capacitor" plates,i.e. the conductive pad, polarizes in order to store charge.

However, once the sponge-filled gel is polarized, it will take time todepolarize. Therefore, long after the current pulse has been applied,the "capacitor" will still retain a voltage of several hundredmillivolts until the conductive pad depolarizes, and the "capacitor"discharges. Since effective monitoring must be sensitive enough to pickup a signal on the order of one millivolt from a patient's body, thecontinued storage of charge, resulting in a voltage of several hundredmillivolts remaining across the "capacitor" plates, may drown out thesignal from the patient's body, making stimulation and monitoring fromthe same electrode, difficult, if not impossible, until the electrodedepolarizes.

A problem with using multiple sets of electrodes is that it iscumbersome and unwieldy since the wires from the many sets often becometwisted. The twisting of the wires is problematic since it may result indelays in delivering necessary emergency care to a patient.

Another problem is that the multiple sets of electrodes will move, andit will be difficult to ensure consistent placement of the electrodeswith respect to one another. Without consistent placement of themonitoring electrodes, the visual display of a patient's heart conditionmay be heavily biased since it is heavily dependent on the placement ofthe monitoring electrode with respect to the stimulating electrode.

Prior art electrodes also suffer from problems unrelated to sequentialor multiple use. For example, prior art electrodes do not typicallyadhere properly to a patient's skin since only a small portion of thesurface area of the electrode, the ring of flexible adhesive attached tothe gel-filled foam, is available for adhering to the patient's skin. Asa result, the electrode will typically adhere poorly, causing thedefibrillating or pacing electrical impulses to pass through the skin inthe few places where contact has actually been made, leading to skinburns. Also, these electrodes may tend to move, and any movement of themonitoring electrode while monitoring is being performed will interferewith and alter the electrical impulses being received from the patient'sbody by introducing biases known as monitoring artifacts, which will inturn lead to inaccurate diagnosis and monitoring of the patient's heartcondition. Moreover, the conducting pad in the prior art electrodes istypically a saline-based, gel-filled sponge, and movement of theelectrode will cause the gel to smear over the surface of a patient'schest. The smearing of the gel further limits the ability of a singleset of prior art electrodes to perform multiple electrical,physiological functions, since the smearing of the conductive gel willresult in an electrical interaction between the electrical impulsesbeing delivered and received from a patient's heart in support of thestimulation and monitoring functions. Also, besides smearing, the priorart gels will leave a residue on the patient's skin, and they may take along time to depolarize which further limits the ability of a single setof prior art electrodes to perform multiple electrical, physiologicalfunctions.

Accordingly, it is an object of the present invention to provide anelectrode having multiple conductive polymer pads which enable a singleset of electrodes to perform multiple electrical, physiologicalfunctions at or about the same time, such as stimulating and monitoringof a patient's heart.

SUMMARY OF THE INVENTION

To achieve the foregoing objects, and in accordance with the purpose ofthe invention as embodied and broadly described herein, there isprovided a multi-pad, multi-function electrode wherein each pad iscomposed of a conductive polymer known as a hydrogel. The hydrogel isalso optionally inherently adhesive to achieve superior adhesion to apatient's skin over its entire surface area, is rubber-based and hencedoes not smear or leave a residue on a patient's body, and depolarizesfaster and has lower impedance compared with typical prior artsaline-based gels.

Since each electrode has multiple polymer pads, a set of such electrodescan better perform multiple electrical, physiological functions, such asstimulation and monitoring of a patient's heart, compared with a singleset of prior art electrodes. In fact, the use of multiple polymer padsmakes monitoring and pacing of a patient's heart from the same set ofelectrodes possible for the first time.

Since the hydrogel is optionally inherently adhesive, each pad can alsoachieve superior adhesion to a patient's skin over its entire surfacearea, eliminating or minimizing the problem of burns, poor adhesion, andmovement associated with prior art electrodes. Also, since the hydrogelhas lower impedance compared to the prior art gels, less voltage will berequired to deliver a current pulse through the electrode in order tostimulate a patient's heart, so that the voltage generator and thecardiac system of which the electrode is a part can be smaller, morecompact, and less costly.

Finally, the fact that the hydrogels depolarize faster compared to theprior art gels, further contributes to the performance of multipleelectrical, physiological functions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing an exploded view of an electrodeincorporating the teachings of the subject invention;

FIG. 2 is a drawing showing an assembled view of an electrodeincorporating the teachings of the subject invention; and

FIG. 3 is a block diagram of a cardiac system incorporating an electrodeof the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A diagram of an electrode incorporating the teachings of the subjectinvention is illustrated in FIG. 1. As indicated in the Figure, theelectrode advantageously comprises peelable cover 1, stimulating polymerpad 2, monitoring polymer pad 3, stimulating metal foil 4, monitoringmetal foil 5, plastic foam cover 6, stimulating insulated wire 7,monitoring insulated wire 8, and wire retainer/label 9. An object of theelectrode is to perform multiple electrical, physiological functionsfrom a single set of electrodes at or about the same time through theuse of multiple polymer pads. In the example illustrated in FIG. 1, onepad is provided to deliver electrical impulses to a patient's heart inorder to stimulate it, while another pad is provided to receiveelectrical impulses from the patient's heart in order to monitor it. Theinvention, however, is not limited to this specific example, and isinstead meant to encompass an electrode for performing any number ofelectrical, physiological functions at or about the same time from asingle set of electrodes, including but not limited to stimulating,defibrillating, pacing, and monitoring of a patient's heart aspreviously described, and also electrical therapeutic stimulation of apatient's muscles. The invention is also meant to encompass an electrodehaving more than two conductive polymer pads.

The peelable cover is advantageously attached to the polymer pads tokeep any foreign material off of the surface of the pads, and can bepeeled off when the electrode is about to be applied to a patient'sskin.

The stimulating and monitoring polymer pads are preferably physicallyseparated from one another in the layout of the surface of theelectrode, as indicted in FIG. 2 (which uses the same identifyingnumerals as FIG. 1), in order to isolate the delivery and receipt ofelectrical impulses in support of the stimulating and monitoringfunctions.

The stimulating and monitoring pads are advantageously attached to thestimulating and monitoring metal foils, respectively, which are in turnattached to the plastic foam cover, which acts as a foam backing to bothmetal foils. The plastic foam cover has holes in it, exposing thestimulating and monitoring metal foils, and the stimulating andmonitoring insulated wires have exposed ends which are inserted into theholes and electrically coupled to the metal foils. The plastic cover issandwiched between the foils and the wires.

In the example of FIG. 1, the hydrogel pads are advantageously 25 mils(1 mil equals 0.001 inch) thick. Moreover, the metal foils arepreferably comprised of tin since the foil will be in contact with theconductinve polymer pads, and other metals will tend to corrode whenplaced in contact with the pads. Also, in the example of FIG. 1, the tinfoil is advantageously 3 mils thick.

The foam backing is advantageously comprised of a rubber closed-cellfoam such as VOLARA. The foam is advantageously closed-cell, i.e., hasair pockets completely surrounded by foam, so that no foreign materialcan get through it. This is to be contrasted with an open-cell materialsuch as a sponge, which allows foreign material such as water to passcompletely through it. In addition, the foam backing is advantageouslycovered with a medical grade adhesive which will enable the foam backingto adhere directly to the metal foils, and to the human body in thoseareas which are not adhered to the metal foil covers of the conductivepolymer pads. In the example of FIG. 1, the foam backing isadvantageously 1/16 of an inch 0.062 inches) thick, and the foam backinghas two holes to allow exposure of the stimulating and monitoring metalfoil coverings. As mentioned earlier, the stimulating and monitoringinsulated wires have exposed ends, which are inserted into the holes andelectrically coupled to the stimulating and monitoring metal foilcovers, respectively.

In the example of FIG. 2, the dimensions of the electrode are providedin centimeters (cm.). As indicated in the Figure, the face of theelectrode has an irregular shape and advantageously has a height of 14cm. Moreover, the stimulating pad is also irregularly shaped andadvantageously has the dimensions indicated in the Figure. In addition,the monitoring pad is advantageously shaped as a circle with a diameterof 2 cm. In this example, the distance between B and A is 1.0 cm.,between C and A, 2.0 cm., between D and A, 2.53 cm., between E and A,7.0 cm., between F and A, 7.47 cm., between G and A, 12.0 cm., andbetween H and A, 13.0 cm. In addition, dimension I in this example is0.5 cm. (2 places, J, 2.0 cm., K, 5.0 cm., and L, 5.0 cm.)

These numerical dimensions are intended to define only one embodiment ofthe subject invention, are intended to be exemplary dimensions only, andare not meant to be limiting. Therefore, other embodiments are intendedto be within the scope of the invention.

Finally, the wire retainer/label is placed over the holes in the foambacking after the exposed ends of the wires have been inserted andelectrically coupled to the metal foils. The wire retainer is coatedwith an adhesive so that it will adhere to the foam backing and reducestrain on the wires. Also, the monitoring and stimulating insulatedwires are bonded together to prevent their becoming twisted with oneanother.

The multiple pads are preferably physically spaced from one another. Thephysical isolation of the pads from one another largely makes itpossible for a single set of electrodes to more efficiently performmultiple electrical, physiological functions at or about the same timefrom a single set of electrodes. The reason for this is that one or moreconductive pads are devoted exclusively to monitoring, and there is noneed to wait for these pads to depolarize since they will never be usedfor the stimulating function. Because a single set of electrodes isused, the problems of twisted leads and consistent placement associatedwith the prior art use of multiple sets of electrodes is eliminated.Compared with the prior art sequential use of a single set ofelectrodes, defibrillating and monitoring from a single set ofelectrodes can be performed at or about the same time, and pacing andmonitoring from a single set of electrodes is possible for the firsttime.

The pads are preferably composed of conductive, polymer compounds knownas hydrogels which are the result of recent, significant advancements inconductive gel technology. A recent article providing more informationabout the conductive polymers is R. Kaner and A. MacDiarmid, PlasticsThat Conduct Electricity, Scientific American, Vol. 258, No. 2 (Feb.1988), which is herein incorporated by reference.

The hydrogels offer several advantages over existing saline-based gels.First, the hydrogels have the consistency of rubber, eliminating thesmearing problem associated with prior art gels. In addition, because oftheir rubber-like consistency, the hydrogels have a longer shelf lifethan the prior art gels, and they do not leave a residue once they areremoved from contact with a patient's skin. Finally, the hydrogels neednot be integrated with a sponge in order to achieve their shape.

Second, the hydrogels used for the electrodes can be chosen to beinherently adhesive, so that the pads will adhere to a patient's skinover their entire surface area compared with the ring of adhesivesurface provided with prior art electrodes. As a result, the pads willadhere better, eliminating the problem of burning and electrode movementduring monitoring associated with prior art electrodes.

Third, the hydrogels have better electrical characteristics than theprior art gels. They are lower ia impedance than the present gels, sothat less voltage is required to administer a particular stimulatingcurrent pulse. As a result, the voltage generator in the cardiac systemto which the electrode is integrated, and the entire cardiac system ingeneral, can be made smaller, more compact, and less costly. Also, thehydrogels, because of their different electrochemistry, will depolarizemuch faster than prior art gels. In fact, the hydrogels will typicallydepolarize in one-half the time it takes for a prior art gel todepolarize. The faster depolarization of the hydrogels, theirrubber-like consistency, and their elimination of smearing furthercontribute to the ability to perform multiple electrical, physiologicalfunctions from a single set of electrodes.

As is clear from the above descriptions, a multi-pad electrode forperforming physiological multiple, electrical functions at or about thesame time from a single set of electrodes is described.

A cardiac system for performing multiple, electrical physiologicalfunctions at or about the same time is illustrated in FIG. 3. As shownin the Figure, the system preferably comprises stimulating means 101,monitoring means 102, and electrode means 103. In the example of FIG. 3,stimulating means 101 further comprises defibrillator 201, defibrillatorpaddles 202, defibrillator input plates 203, and externalpacemaker/defibrillator pass-through 204. As indicated in the Figure,the defibrillator paddles are advantageously electrically coupled to thedefibrillator, the defibrillator input plates are advantageouslyelectrically coupled to the pass-through, which in turn isadvantageously electrically coupled to the monitoring means. Finally,the electrode means is advantageously electrically coupled to thepass-through.

In the example of FIG. 3, defibrillator 201 is a conventionaldefibrillator (typically a LIFEPAK 5 by PhysioControl) which deliversdefibrillating energy by means of defibrillator paddles 202. Inaddition, monitoring means 102 is a conventional ECG monitor. Electrodemeans 103 are preferably a single set of multi-pad, multi-functionelectrodes of the subject invention described earlier.

Pass-through 204 is an asynchronous external cardiac pacemaker thatprovides for the combined use of the most important aspects of emergencycardiac treatment. The device is advantageously approximately 6"×2"×3"and contains the circuitry for an external cardiac pacemaker. Moreover,it is designed to mount on top of industry standard defibrillators toenhance the treatment of heart attack victims, and the device isdesigned to operate for 2-3 hours on two disposable 9V alkalinebatteries. It advantageously has three pacing rates, 60, 80 and 100beats per minute, and two pacing amplitudes, 100 and 150 milliamperes(mA). Pacing or defibrillating current is delivered through theelectrodes. External cardiac pacing is an old and proven technique forinitiating a heart contraction.

The defibrillator input plates located on the top of the pass-throughare spring loaded and provide the ability to defibrillate and pacethrough the same set of electrodes. When one plate is depressed, anintermittent tone is sounded. When both plates are fully depressed, thetone becomes constant, indicating that both plates are down and thatdefibrillation may follow. Defibrillating energy is then generated anddelivered by the defrillator through the pass-through and to the patientthrough the electrodes. The plates are designed to be depressed by thepaddles of any defibrillator with no gel required. After the plates havebeen depressed by means of the defibrillating paddles, the plates willspring back up and reconnect the pacemaker circuitry to the patient.When both plates are not fully depressed, pacing may follow. Pacingenergy is then generated and delivered by the pass-through to theelectrodes and ultimately the patient.

The pass-through also provides a connection for a two lead ECG monitorthrough the pass-through straight to the electrodes. The monitor signalwill advantageously pass through the pass-through whether or not it isturned on. Also, no manipulation or alteration of the monitor signal isperformed inside the pass-through.

Typical usage of the cardiac system will first consist of the use of theelectrodes for monitoring which will enable the determination oftreatment. This is typically followed by the initiation of externalcardiac pacing through the same set of electrodes. As indicated above,the pass-through will generate and deliver external cardiac pacingenergy through the electrodes to a patient automatically when both inputplates are not fully depressed. Should defibrillation be necessary, thepaddles will be firmly pressed against the plates until both aredepressed and the resultant tone is constant, and the defibrillator willgenerate and deliver defibrillating energy through the electrodes to thepatient. Additional monitoring can then be performed, and additionaltreatment in the form of external pacing can be immediate.

Additional advantages and modifications will readily occur to thoseskilled in the art. The invention in its broader aspects is not,therefore, limited to the specific details, representative methods, andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the spirit or scope ofapplicant's general inventive concept.

What is claimed is:
 1. A non-invasive electrode comprising:at least twospaced conductive polymer pads, each pad having a surface arranged to beplaced in contact with a patient, for stimulating and monitoring thepatient's heart at or about the same time wherein at least a first oneof said conductive polymer pads has an area determined effective forcardiac stimulation, and is adapted for receiving first electricalimpulses from stimulating means, and delivering said first electricalimpulses to the patient's heart, while at least one other of saidconductive polymer pads is adapted for receiving second electricalimpulses from that patient's heart and delivering said second impulsesto monitoring means at or about the same time said first pad isdelivering said first electrical impulses, the other pad being spacedfrom said first pad by a distance determined effective to substantiallyisolate the first electrical impulses from the second electricalimpulses; substantially non-conducting backing means for integrallyconnecting said first and other pads; means for electrically couplingsaid first pad to said stimulating means; and means for electricallycoupling said other pad to said monitoring means.
 2. The electrode ofclaim 1 wherein said means for electrically coupling said first pad tsaid stimulating means comprises means for electrically coupling saidfirst pad to defibrillating means.
 3. The electrode of claim 1 whereinsaid means for electrically coupling said first pad to said stimulatingmeans comprises means for electrically coupling said first pad to pacingmeans.
 4. A non-invasive electrode comprising:at least two spacedconductive polymer pads, each pad having a surface arranged to be placedin contact with the patient, for pacing and monitoring the patient'shear at or about the same time, wherein at least a first one of saidconductive polymer pads has an area determined effective for cardiacpacing, and is adapted for receiving first electrical impulses frompacing means and delivering said first impulses to the patient's heart,while at leas one other of said conductive polymer pads is adapted forreceiving second electrical impulses from that patient's heart anddelivering said electrical impulses impulses to monitoring means at orabout the same time said first pad is delivering said first electricalimpulses, the other pad being spaced from said first pad by a distancedetermined effective to substantially isolate the first electricalimpulses from the second electrical impulses; substantiallynon-conducting backing means for integrally connecting said first andother pads; means for electrically coupling said first pad to saidpacing means; and means for electrically coupling said other pad to saidmonitoring means.
 5. A cardiac system comprising:at least a pair ofelectrodes wherein at least a first one of said electrodes isnon-invasive, and has at least two spaced conductive polymer padsintegrally connected by means of a substantially non-conducting backingwherein at least a first one of said pads has an area determinedeffective for cardiac stimulation, and is adapted to receive firstelectrical impulses from stimulating means and deliver said firstelectrical impulses to a patient's heart, while at least one other ofsaid pads is adapted to receive second electrical impulses at or aboutthe same time from that patient's heart and to deliver said secondelectrical impulses to monitoring means; stimulating means for producingsaid first electrical impulses; and monitoring means for receiving saidsecond electrical impulses.
 6. The system of claim 5 wherein saidstimulating means is defibrallating means.
 7. A cardiac systemcomprising:at least a pair of electrodes wherein at least a first one ofsaid electrodes is non-invasive, and has at least two spaced conductivepolymer pads integrally connected by means of a substantiallynon-conducting backing wherein at least a first one of said pads has anarea determined effective for cardiac pacing, and is adapted to receivefirst electrical impulses from pacing means and to deliver said firstelectrical impulses to a patient's heart, while at least one other ofsaid pads is adapted to receive second electrical impulses at or aboutthe same time from that patient's heart and to deliver said secondelectrical impulses to monitoring means; pacing means for producing saidfirst electrical impulses; and monitoring means for receiving saidsecond electrical impulses.
 8. A cardiac system comprising:at least apair of electrodes wherein at least a first one of said electrodes isnon-invasive, and has at least two spaced conductive polymer padsintegrally connected by means of a substantially non-conducting backingwherein at least a first one of said pads is adapted to receive firstelectrical impulses and to deliver said first electrical impulses to apatient's heart, while at least one other of said pads is adapted toreceive second electrical impulses at or about the same time from thatpatient's heart and to deliver said second electrical impulses tomonitoring means means for generating defibrillating electricalimpulses; means for generating pacing electrical impulses; couplingmeans for delivering said first electrical impulses to said first pad,said first electrical impulses comprising a selected one of saiddefibrillating electrical impulses and said pacing electrical impulses;and monitoring means for receiving said second electrical impulses.
 9. Aprocess for stimulating and monitoring a patient's heart at or about thesame time utilizing a non-invasive electrode having at least two spacedconductive polymer pads, wherein at least a first one of said pads hasan area determined effective for cardiac stimulation, comprising thesteps of:delivering stimulating electrical impulses to said patient'sheart through said first pad; and receiving electrical impulses at orabout the same time from said patient's heart through at least one otherof said pads.
 10. The process of claim 9 wherein said delivering stepcomprises delivering defibrillating electrical impulses.
 11. The processof claim 9 wherein said delivering step comprises delivering pacingelectrical impulses.
 12. The process of claim 9 further comprising thestep of displaying a representation of said received electricalimpulses.